When a motor vehicle runs linearly, both wheels of the motor vehicle are driven at the same rotation speed. However, when the motor vehicle turns a bend in a road, an outer wheel having a larger turning radius rotates faster and further than an inner wheel having a smaller turning radius to achieve smooth turning without slipping. Therefore, the inner and outer wheels are driven at different rotation speeds.
As described above, a differential device is installed at a vehicle axel to transmit power of an engine to wheels and adjusts rotation speeds at opposite wheels differently according to the bad applied to the wheels.
The conventional differential device includes a differential gear that receives the power of a transfer shaft installed at a transmission, a differential case assembled with the differential gear and rotating, a pinion gear rotatably installed at the differential case, a pinion shaft installed to fix the pinion gear to the differential case, and a side gear installed on an output shaft and rotating in gear with the pinion gear.
In the conventional differential device, since a connection part connected to a driving shaft of a driving part is integrally formed with a driving axel, it is difficult to easily adapt to a change in the driving axel. In particular, in a case of recently actively developed electric vehicles using a driving motor, the driving motor may be connected to a driving pinion by a direct-type driving method, a compressive or tensile bad may be applied to a rotator of the driving motor due to an external force generated at the driving axel, which may result in a shorter life of the driving motor.